IIRC, there was no "social" part of the media. It was just random links to other sites. Most of which also had zero social media factor. SU was just curiosity.
Digg : 2004, not that much before reddit. Stumbleupon and hotornot.com both predate these by a lot. There was also Myspace before Digg, and Tribes before that.
Milk inflation is not that significant. Five dollars of milk in 2000 will cost you 6.51 USD today[0]. It's actually lower this year than it was in 2014[1].